Jacko,
I was speaking to the section width of the 275R/60/15s I bought. With a 4.25in Back Space tire didn't clear spring at 11.2 section width.
I won't run 'universal spacers'. Can't find drilled 5 on 4 solid spacers.
It's all about back spacing.
Easy to measure drum face to spring and use simple math from there for clearance based on tire OD/Tread width/actual (not advertised) back space.
Section widths vary a little by manufacturer.